The present invention relates to a boom control device. In particular, the invention relates to an intelligent boom control device.
Various construction vehicles with boom are widely used. The boom is a device including at least three boom sections hinged by horizontal joint shafts. Each boom section can rotate a considerable angle around the joint shafts. Meanwhile, the whole boom is fixed to a machine frame by rotary platform, which can bring the whole boom to rotate around the upright axis vertical to the horizontal plane for 360 degree. A typical application of this boom is to act as construction apparatus, for example to move objects from one spot to another and hang up them. At present, such boom devices are widely applied to construction site for concrete placing and other like works.
For example, concrete pump truck with feed spreading boom is a typical construction vehicle with boom. Such vehicle is applied to concrete placing according to the operating control requirements at construction sites that need concrete placing. When boom device is applied for concrete placing and the like, control requirement for the boom device is relatively strict, especially there is a need to accurately control movement track of boom end.
FIG. 1 shows a boom structure of such concrete pump truck. The structure and control principle of this boom will be described with reference to FIG. 1 hereinafter.
As shown in FIG. 1, a concreter pump truck 8 includes a boom 9, and a machine frame 10 formed of automobile chassis.
In FIG. 1, the boom 9 is composed of five boom sections 12-16 hinged with each other, and rotary platform 11 driven by hydraulic motor and being rotatable around upright axis 18. The five boom sections are called first arm 12, second arm 13, third arm 14, fourth arm 15 and fifth arm 16, each boom section is controlled by a corresponding one of hydraulic oil cylinders 31-35, respectively. The action of which can revolve the respectively controlled boom section around their respective joint shafts. Meanwhile, the rotary platform 11 may also be driven to rotate by hydraulic rotary motor 30 (not shown in FIG. 1, please refer to FIG. 2). During construction, by means of the movement of operating handle of a remote controller, operator can control the gesture of the boom and the rotation of the rotary platform so as to move the boom end 20 having a terminal hose 17 above the area to be placed with concrete. This terminal hose 17 is connected to a concrete conveying pump, and the concrete is ejected through terminal hose 17 to implement concrete placing.
FIG. 2 shows the movement control system of the boom shown in FIG. 1 in the prior art. This system includes a remote controller 40 which can transmit wireless remote control signal, a receiver 41 fixed to the vehicle, an electrical hydraulic control element, i.e., electric proportional multi-way valve 52, the hydraulic oil motor 30, and an executive unit 53 composed of the hydraulic oil cylinders 31-35.
As shown in FIG. 2, the remote controller 40 includes six proportional rockers 42-47 which may be adjusted to and fro along a primary adjustment direction and may transmit remote control signals in analog quantity for controlling the rotary platform and the respective boom sections, respectively. The remote control signals are transmitted to the receiver 41 fixed to the vehicle by radio wave 51 at a certain frequency. The remote controller 40 also includes a row of other switch mechanisms 48, 49, 49′, 49″, and when they are operated other related remote control radio signals are transmitted by radio wave 51 at a certain frequency to radio receiver 41. When adjusting the working position of the boom end, if an action of a certain boom section or a rotary action is needed, the control command can be transmitted by manipulating the corresponding proportional rockers 42-47 forward or backward. After receiving the radio signals, the receiver 41 outputs PWM driving signals corresponding to each boom section or the rotary platform to electric proportional multi-way valve 52 so as to perform control. The electric proportional multi-way valve 52 includes electric proportional valves 56-60 for driving hydraulic oil cylinders 31-35, respectively; and further includes an electric proportional valve 55 for driving a two-way oil motor 30. Elongating or shortening the hydraulic oil cylinders 31-35 makes the corresponding boom sections pivot about the joint shafts restrictedly. A rotation of the oil motor 30 can make the whole boom 9 rotate around the upright axis 18 by a deceleration mechanism.
The above-described is a typical manner for implementing the action of a single section boom. This embodiment does not require a boom measuring and sensing system as well as a coordinate transformation system supported by computer, however, it cause complicated operation. For example, if assuming in FIG. 1 that terminal hose 17 needs to be moved from the position shown in the figure to position A without changing the height of the boom end 20, the operator has to move at least two or more boom sections. Therefore, operator needs to control two of the rockers 43-47 to move the hose 17 from the position shown in the figure to point A without changing the height. However, to accomplish this operation quickly, even an experienced operator can hardly keep the height of the boom end 20 during the process of movement.
In the prior art, a number of technical solutions to implement automatic control of the boom movement using automatic control technology have been proposed to solve the above-described problem of moving multi-sections boom without changing its operation height. These technique solutions implement a simply and easy control of the boom by means of a boom measuring and sensing system as well as a coordinate transformation system supported by computer.
For example, German Patent No. DE-A-4306127 (see also U.S. Pat. No. 6,862,509) owned by Putzmeister Company regarding boom operating device provides a boom operating device on which a cylinder (polar) coordinate system is defined, the cylinder coordinate system has three coordinate axes: ψ, r and h (refer to FIG. 1). The three coordinate axes correspond to boom rotation (ψ), boom elongating or shortening (r) and boom height lifting and lowering (h).
In the patent owned by Putzmeister Company, a rocker having three primary adjustment directions is used to implement the control according to three directions of the cylinder coordinate mode defined above. Each primary adjustment direction of the rocker corresponds to one coordinate axis. When an operator controls the rocker to move, a signal corresponding to the related coordinate axis is generated according to the moving direction of the rocker, and through a computation of a computer, control components corresponding to the relative rotation of respective boom sections and the rotation of the whole boom are generated so that the boom can be controlled to move in the defined coordinate system according to the action of the rocker. The control components at the three coordinate axes can also be combined so that an operating/control action can transmit control signals regarding more than two coordinate axes direction to implement control of the boom end in a simple but accurate way, especially control of the coordinate axes parallel to the horizontal plane.
In the intelligent boom control device provided in the above-described patent, the coordinate system defined therein is of great intuitionistic so that it is very convenient for an operator to move the boom end from one position to another in the space.
However, the intelligent boom control device described above still has obvious drawback.
As for a typical boom application such as concrete pump truck, when placing concrete, how to move the boom end from one space position to another space position is only one of the concerned problems, moreover it is needed to accurately control the movement track of the boom end, so that the correct placing execution be implemented.
During the placing execution, placing along the direction of straight lines perpendicular to each other is the typical placing method. In this placing method the movement track of the boom end is required to be straight line.
In the cylinder coordinate mode provided in the prior art, the movement track of the boom end is usually an arc line rather than a straight line because of the adaptation of the rotation axis. Please refer to FIG. 3, this figure shows a formation process of the movement track accomplishing the movement from point A in a plane to point D in the same plane in the cylinder coordinate mode described above. In this example, it assumes that movement in the direction of height axis h is not required, i.e. the movement from point A to point D is at the same height.
FIG. 3a shows projection of initial position of the boom to the horizontal plane. At this time, the boom end N is at point A in the cylinder coordinate plane with rotary platform as origin O. The present operating requirement is shown in FIG. 3b, i.e. moving the boom end N from current coordinate point A to point D, the required track is a length of straight line from point A to point D shown in FIG. 3b. However, in the cylinder coordinate mode, actual track of the boom end N is not a straight line.
Please refer to FIG. 3c, this figure shows a track of the boom end in the cylinder coordinate mode. In the present cylinder coordinate mode, the movement track of the boom end is decomposed to the ψ axis movement and r axis movement. Decomposing the movement in this manner, the boom end N will rotate about the ψ axis in the axis direction, and move on the r axis, i.e., the straight line in the elongating direction MN of the boom at the same time. In the original state, the end N of the boom MN coincides with point A, i.e. the projection of the boom MN to the horizontal plane is OA; the projection of the boom to plane is OB at next time unit because the boom rotates and elongates at the same time during its movement. Similarly, the projection of the boom to plane is OC at further next time unit, and the projection of the boom to plane is OD when moving to the terminal target position D. In this way, the track of the projection of the boom end N on the plane is a length of polygonal line from point A to point D. This line is a track formed from only few points at time units. In fact, the track of the boom end N from point A to point D is a length of arc with increasing radius. Such movement track doesn't have negative effect on general construction operating. However, in the case of cement placing and the like where control requirement for movement track of the boom end N is relatively high, the above movement track can't satisfy the operating requirement.